Errors in Create a ListView widget --WAB Sample Code--?

FrancescoTonini2

I am following line by line the setup of a custom ListView widget from the official ESRI sample code page:

Create a ListView widget—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers 

• Under "Create a Widget Folder Structure": 

               ...

               4)  Register the widget in the list.json at path/to/WAB/client/stemapp/widgets.

              ...

 

               Is this list.json an error? There is NO such file inside ~client/stemapp or ~client/stemapp/widgets. Beside, do I                really have to "register" the widget? In order for it to be available to WAB, I thought it simply needs to be                copy/pasted into ~client/stemapp/widgets...